Entrained-flow gasification of biomass as slurry

ABSTRACT

A method for entrained bed gasification of biomass is provided, wherein pure biomass is first torrefied then milled and the torrefied and milled biomass is introduced to the gasification process with a fluid as a slurry. An energetically favorable process is described using the combination of torrefaction, milling and mixing with a liquid, preferably residual products from a subsequent synthesis process, but also other available suitable materials.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2008/062794, filed Sep. 24, 2008 and claims the benefit thereof. The International Application claims the benefits of German application No. 10 2007 050 895.8 DE filed Oct. 24, 2007. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The subject matter of the application relates to a method for the entrained-flow gasification of biomass.

BACKGROUND OF INVENTION

Feeding in (solid) biomass such as wood, straw, miscanthus, etc. into an entrained-flow gasifier according to the dense phase conveying method is energetically unfavorable due to the high carrier gas flow rate and generally makes such a method uneconomic.

To date there are no application cases in which biomass in solid form is gasified exclusively in the entrained-flow gasifier. Only admixing with coal is known in the prior art.

SUMMARY OF INVENTION

The object underlying the invention is to disclose a method for the entrained-flow gasification of solid biomass which is energetically more favorable with regard to the dense phase conveying method.

The object is achieved by means of the features of the claims.

According to the inventive method, biomass is first torrefied (torrefaction process), subsequently ground into small particles with relatively little energy expenditure, then mixed with a liquid and pumped into the entrained-flow gasifier. In particular in the case of methods for generating synthetic fuels there is a case for using a part of the generated fuel or accumulating liquid residue materials such as e.g. paraffins. Other available liquid media such as water, oils, glycerin, methanol, liquid CO2, etc. are also possible, however. By means of the method according to the invention, which may be described by the term “torry slurry feed”, the entrained-flow gasification of pure biomass is rendered energetically favorable.

Through the combination of torrefaction, milling and mixing with a liquid—ideally residual products from downstream synthesis processes, but also other available liquid substances—the biomass sector can also be opened up for entrained-flow gasification, something which previously was either not possible or only possible in combination with primarily fossil-fired installations.

Advantageous developments of the subject matter of the application are set forth in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the application is explained in more detail below to an extent necessary for understanding as an exemplary embodiment with reference to a figure, in which:

FIG. 1 shows a schematic representation of an apparatus implementing the method according to the invention.

DETAILED DESCRIPTION OF INVENTION

In a first stage 1, which may be described as “biomass torrefaction”, biomass 1.1, such as e.g. wood, straw or miscanthus, is torrefied in a torrefaction apparatus 1.2. The torrefied biomass is fed to a mill 1.3, where it is ground into particles that are suitable for the following slurry generation. The particles are supplied via a first inlet to a mixing apparatus 1.4 to which a liquid medium such as water, oils, heavy oil, bio-oil, glycerin, methanol, liquid CO2, paraffin, tar etc. is supplied via a second inlet. The biomass is mixed with the liquid medium in the mixing apparatus to produce a slurry.

The slurry is fed to a second stage 2, which may be described by the term “gasification”, where it is supplied by means of a slurry pump 2.1 to an entrained-flow gasification reactor 2.2 together with an oxidizing agent O2 containing free oxygen. A partial oxidation of the supplied slurry takes place in the entrained-flow gasification reactor in a flame reaction under high pressure of up to 8 MPa and temperatures of up to 1800 degrees Celsius, producing raw gas 2.3, with the accumulating residual product 2.4 being discharged downward. The raw gas is cleaned in a raw gas cleaning apparatus 2.5.

The cleaned raw gas is fed to a third stage 3, which may be described by the term “GasCleanUP/Synthesis”, where a synthesis is performed to produce a product 4 such as e.g. diesel, gasoline, methanol, dimethyl ether (DME), paraffin, water, liquid CO2 or oil.

In a special embodiment of the invention a fraction of the product 4 is fed to the mixing apparatus 1.4 as a liquid medium via a return feed line 5.

In a special embodiment of the invention residual products from downstream synthesis processes are fed to the mixing apparatus 1.4 as a liquid medium via a return feed line 5.

In a special embodiment of the invention a fraction of the recycled product 4 or, as the case may be, residual product is supplied as one portion to the mixing apparatus 1.4 and a medium supplied to the arrangement from outside as a liquid medium as the remaining portion; in this case the recycled (residual) product and the externally supplied medium can be different, e.g. the recycled (residual) product can be represented by dimethyl ether and the externally supplied medium by glycerin. 

1.-7. (canceled)
 8. A method for entrained-flow gasification of a biomass, comprising: torrefying the biomass; and milling the biomass, wherein the torrefied and milled biomass is fed together with a liquid as slurry to the gasification process.
 9. The method for entrained-flow gasification as claimed in claim 8, wherein a fraction of a recycled synthetic product generated in the gasification process is used as the liquid.
 10. The method for entrained-flow gasification as claimed in claim 8, wherein a recycled residual product generated in a synthesis process following the gasification process is used as the liquid.
 11. The method for entrained-flow gasification as claimed in claim 9, wherein the recycled synthetic product generated in the gasification process or the recycled residual product is used as one portion of the liquid, and a liquid medium supplied from outside as a remaining portion of the liquid.
 12. The method for entrained-flow gasification as claimed in claim 11, wherein the residual product and the liquid medium are different.
 13. The method for entrained-flow gasification as claimed in claim 12, wherein the residual product is dimethyl ether and the liquid medium is glycerin.
 14. The method for entrained-flow gasification as claimed in claim 8, wherein water, oils, paraffin, glycerin, methanol or liquid CO2 is used as the liquid.
 15. The method for entrained-flow gasification as claimed in claim 8, wherein wood, bark, straw, miscanthus or another renewable raw material is used as the biomass.
 16. The method for entrained-flow gasification as claimed in claim 8, wherein an arbitrary mixture of wood, bark, straw, miscanthus and other renewable raw materials is used as the biomass. 